A field trip to the Reef Islands of the Solomon Islands will be conducted to confirm observations we have made concerning the distribution of HBsAg and anti-HBsAg in other areas of the Solomon Islands. In these populations family contact is modified by young boys and men living in the Single Men's House. Here genetic and family infectious processes can be separated. A census will be prepared and all individuals will be tested for HBsAg and anti-HBsAg in the field. Serum samples will be returned to Bethesda and tested for HBeAg and anti-core. The main observations to be confirmed are: (1) An excess of males among siblings of HBsAg carriers. (2) A lack of clustering of HBsAg carriers among siblings of HBsAg carriers. (3) A failure of the distribution of HBsAg carriers to conform to that of an autosomal recessive gene. (4) An increased susceptibility of young children to becoming HBsAg carriers. (5) A strong correlation between youth and HBeAg.